The present inventions are related to systems and methods for accessing data from a storage medium, and more particularly to systems and methods for retrying a previously failed data access from a storage medium.
A typical storage device includes a magnetic storage medium that includes information that is magnetically represented on the storage medium. A head is disposed in relation to the storage medium that senses the magnetically represented information and provides an electrical signal representing the information. This electrical signal is ultimately passed to a data detection circuit that performs one or more data detection processes in order to recover the information originally written to the storage medium. In some cases, the data processes fail to converge on the originally written information due to an error on either the storage medium or in the interface between the head and the storage medium. In such a case, an attempt to retry a read of the affected area is triggered.
Turning to FIG. 1, a flow diagram 100 depicts a prior art approach for performing a data retry. Following flow diagram 100, a data location on a storage medium from which data is to be retrieved is identified (block 110). The head and/or storage medium are moved relative to one another such that the head is located in proximity to the identified location and the data is retrieved from the storage medium (block 120). Analog processing is performed on the received data (block 130), and an analog to digital conversion is performed on the processed data (block 140). The retrieved digital data is then processed using a data decoding/detection technique to recover the original data (block 150).
It is determined whether the applied data decoding/detection technique converged on the data originally written to the storage medium (block 160). This determination may be done on a sector basis. Thus, when a failure to converge is identified it is considered a sector failure. Where a sector failure is not indicated (block 160), the data resulting from the decoding/detection process is provided as an output (block 170). Alternatively, where a sector failure is indicated (block 160), a data access retry is selected (block 180). When a retry is selected (block 180), one or more data receiving parameters may be modified (block 190) and the head and storage medium mechanically moved relative to each other to start the process of re-reading the data anew from the storage medium and processing the re-read data using the modified parameters. In some cases, it may take a large number of retries before the data is finally read accurately, with each retry requiring a mechanical repositioning of the head relative to the storage medium. As such, performing a large number of retries can require a substantial amount of time, which in many cases is unacceptable. A timeout period is often used to limit the number of retries. Where none of the many retires succeeds within the timeout period, the storage device may be failed.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for performing a data access retry.